Self-tensioning flexible printing plate

ABSTRACT

A flexible printing plate is disposed on the surface of a rotating printing cylinder. The leading edge of the printing plate is secured to the printing cylinder so the leading edge is fixed in the direction toward the trailing edge of the printing plate by the engagement between a transversely elongated claw and a transversely elongated hook. The trailing edge of the printing plate is secured to the printing cylinder by a ratchet arrangement so the trailing edge is fixed in the direction toward the leading edge and is movable in the direction away from the leading edge by the engagement between one of a plurality of transversely elongated parallel serrations and a transversely elongated hook. As a rotating blanket cylinder disposed adjacent to the printing cylinder presses against the printing cylinder, the printing plate is tensioned. The hooks are set in from the printing surface of the plate and the portions of the plate between the printing surface and the leading and trailing edges are permanently deformed to angle inwardly toward the hooks. The claw and its hook are keyed to insure transverse registration. The serrations and the claw are parallel to insure circumferential registration.

ilnited States Patent [191 Darnall, ,1 1r.

[ SELF-TENSIONING FLEXIBLE PRINTING PLATE [75] Inventor: John C. Darnall, Jr., Van Nuys,

Calif.

[73] Assignee: The Time Mirrow Company, Los Angeles, Calif.

[22] Filed: Feb. 2, 1971 [21] App]. No.: 111,884

[52] U.S. C1. l0l/4l5.1, 101/401.1

[51] Int. Cl. B4lf 27/06, B41f 27/12 [58] Field of Search 10l/415.l, 378, 395, l0l/40l.l, 382, 383, 384

[56] References Cited UNITED STATES PATENTS 3,362,327 l/1968 Luehrs 10l/415.l

3,590,442 7/1971 Geisinger.. 24/16 PB 2,730,949 l/l956 Mitchell l01/4l5.l

2,990,000 6/1961 Mangus et a1 l0l/4l5.1 UX

3,123,001 3/1964 Perry ..10l/4l5.1

3,203,346 8/1965 Norton et al. 101/415.l X

3,221,654 12/1965 .lernt l0l/4l5.1 X

3,276,365 10/1966 Langer... 10l/4l5.l

3,230,878 l/1966 Perian l0l/4l5.1 X

3,334,897 8/1967 Sharkey 101/217 UX 3,353,481 11/1967 Antonucci i. lO1/415.l UX

3,425,348 2/1969 Hermach et a1. l01/41S.1

3,533,355 10/1970 Wall lOl/4l5.l

Jan. 1, 1974 5 7] ABSTRACT A flexible printing plate is disposed on the surface of a rotating printing cylinder. The leading edge of the printing plate is secured to the printing cylinder so the leading edge is fixed in the direction toward the trailing edge of the printing plate by the engagement between a transversely elongated claw and a transversely elongated hook. The trailing edge of the printing plate is secured to the printing cylinder by a ratchet arrangement so the trailing edge is fixed in the direction toward the leading edge and is movable in the direction away from the leading edge by the engagement between one of a plurality of transversely elongated parallel serrations and a transversely elongated hook. As a rotating blanket cylinder disposed adjacent to the printing cylinder presses against the printing cylinder, the printing plate is tensioned. The hooks are set in from the printing surface of the plate and the portions of the plate between the printing surface and the leading and trailing edges are permanently deformed to angle inwardly toward the hooks. The claw and its hook are keyed to insure transverse registration. The serrations and the claw are parallel to insure circumferential registration.

9 Claims, 5 Drawing Figures SELF-TENSIONING FLEXIBLE PRINTING PLATE BACKGROUND OF THE INVENTION This invention relates to the printing art and, more particularly, to a printing system having a flexible printing plate that is self-tensioning.

A recent development in the printing art is the substitution of a suitable thermoplastic, such as polypropylene, for lead as the printing plate material. My copend ing application, Ser. No. 16,485, filed Mar. 4, 1970, discloses a process that reproduces thermoplastic printing plates in duplicate for short run, multiple press newspaper printing operations. Although a thermoplastic printing plate has the advantage of being lightweight, it is also flexible. Consequently, to make the printing plate rigid, it must be mounted on its printing cylinder in tension. If the printing plate is secured to the printing cylinder with slack, the printing plate will bulge when the blanket cylinder presses against the printing cylinder during operation of the press. The operator effort required to mount a flexible printing plate on the printing cylinder in tension offsets in large part the weight advantage.

SUMMARY OF THE INVENTION The invention involves a flexible printing plate that is secured to a rotating printing cylinder in such a way that the printing plate tensions itself as the blanket cylinder presses against the printing cylinder. The leading edge of the printing plate is secured to the printing cylinder so the leading edge is fixed relative to the printing cylinder in the direction toward the trailing edge of the printing plate. The trailing edge of the printing plate is secured to the printing cylinder by a ratchet arrangement so the trailing edge is fixed relative to the printing cylinder in the direction toward the leading edge and is movable relative to the printing cylinder in the direction away from the leading edge. Consequently, as the blanket cylinder presses against the printing cylinder, the slack in the printing plate is transmitted along the printing plate toward its trailing edge to move the trailing edge away from the leading edge. The result of this movement is to tension the printing plate so it conforms rigidly to the surface of the printing cylinder.

Preferably, the printing plate has a transversely elongated claw extending along its leading edge and a plurality of transversely elongated serrations extending along its trailing edge in parallel relationship to the claw. A front hook extending across the printing cylinder engages the claw to fix the leading edge of the printing plate in the direction toward the trailing edge and a rear hook extending across the printing cylinder engages one of the serrations to fix the trailing edge of the printing plate in the direction toward the leading edge, while permitting the trailing edge to move in the direction away from the leading edge. The front and rear hooks are parallel to the axis of rotation of the printing cylinder. The parallel relationship between the serrations and the claw insures the establishment of circumferential registration of the printing plate on the printing cylinder.

A feature of the invention is the provision of a key arrangement between the front hook and the claw to insure the establishment of transverse registration of the printing plate on the printing cylinder. The key arrangement can comprise a finger at the center of the front hook and a matching notch at the center of the claw.

Another feature of the invention is the permanent deformation of the portions of the printing plate between the printing surface and the leading and trailing edges to angle inwardly toward the hooks, which are set in from the surface of the printing plate. The ends of the printing cylinder under the permanently deformed portions of the printing plate are sloped to match the angle of the permanently deformed portions of the printing plate.

BRIEF DESCRIPTION OF THE DRAWING The features of a specific embodiment of the best mode contemplated of carrying out the invention are illustrated in the drawing, in which:

FIG. 1 is a schematic diagram of a rotary printing press;

FIG. 2 is a sectional side elevation view of a mold for fabricating a flexible printing plate in accordance with the invention;

FIG. 3 is an enlargement of a portion of FIG. 1 showing in detail the leading edge of a printing plate fabricated by the mold of FIG. 2;

FIG. 4 is an enlargement of a portion of FIG. 1 showing in detail the trailing edge of a printing plate fabricated by the mold of FIG. 2; and

FIG. 5 is a sectional view of FIG. '3 showing the key arrangement for establishing transverse registration.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT In FIG. 1, a conventional rotatable printing cylinder 10 and a conventional rotatable blanket cylinder 11 of a rotary press are disposed adjacent to each other. Rigid metallic semi-circular saddles l2 and 13 having a curvature that conforms to the surface of printing cylinder 10 are attached to printing cylinder 10 by conventional clamps, such as those represented schematically at 14, 15, 16, and 17. A motor 20 is coupled through appropriate gearing represented by dashed line 21 to printing cylinder 10 to drive it in a clockwise direction as viewed in FIG. 1. Motor 20 is coupled through appropriate gearing represented by dashed line 22 to blanket cylinder 11 to drive it in a counterclockwise direction as viewed in FIG. 1 at the same angular velocity as printing cylinder 10. A flexible printing plate 23 is mounted on saddle 12 to which it is secured at its leading edge 24 and its trailing edge 25 by means discussed below in connection with FIGS. 3 and 4. Similarly, a flexible printing plate 26 is mounted on saddle 13 to which it is secured at its leading edge 27 and its trailing edge 28 by the same means as printing plate 23. The leading edge of the printing plate is defined as the edge that passes by blanket cylinder 11 first on each revolution of printing cylinder 10 and the trailing edge of the printing plate is defined as the edge that passes by blanket cylinder 11 last on each revolution of printing cylinder 10.

A web 30 of paper to be printed is guided between printing cylinder 10 and blanket cylinder 11. The purpose of saddles l2 and 13 is to adapt the conventional printing cylinder that is designed for thick lead printing plates to plates 23 and 26, which are much thinner. Thus, printing plates 23 and 26 are supported by saddles l2 and 13 respectively such that blanket cylinder 1 1, which has a fibrous resilient surface, presses against the printing surface of printing plates 23 and 26 as printing cylinder rotates. Consequently, the character impressions of the printing surface are transferred to web 30, which is pressed between blanket cylinder 11 and printing plates 23 and 26. Web 30 is maintained in tension upstream and downstream of the point where blanket cylinder 11 and printing plates 23 and 26 press against it. Web 30 is pulled off a rotatably supported paper supply roll 31 by the rotation of printing cylinder 10 and blanket cylinder 11. Upstream tension is maintained on web 30 by a brake shoe 32 that creates a drag on roll 31. Downstream tension is maintained on web 30 by a system of tension rollers such as that designated 33. The components of the rotary printing press described to this point are conventional. The invention concerns an arrangement for securing printing plates 23 and 26 to saddles l2 and 13 respectively and accordingly to printing cylinder 10.

In FIG. 2 an injection mold for fabricating printing plates 23 and 26 is shown. The mold is defined by an upper platen 40, a lower platen 41, and clamping bars 42 and 43. An intermediate mold 44, which could be made in the manner described in my above referenced copending application, is clamped at its ends between bars 42 and 43 and lower platen 41. The upper surface of intermediate mold 44 has character depressions matching the impressions to be formed in the printing plate. The lower surface of intermediate mold 44 is held against lower platen 41 by a vacuum supplied through ports in lower platen 41 (not shown). A thermoplastic material, such as polypropylene, under pressure and in a fluid state is supplied by a source (not shown) through conduits 45 and 46 in upper platen 40 to the interior of the mold. This material depicted at 47 fills the space within the mold to form the printing plate.

A printing surface 48 is formed at the bottom of the printing plate as the thermoplastic material conforms to the depressions of intermediate mold 44. At the leading edge of the printing plate, a transversely elongated claw 49 is formed between bar 43 and upper platen 40. A portion 50 of the printing plate between printing surface 48 and claw 49 angles upwardly. At the trailing edge of the printing plate, a plurality of transversely elongated, parallel serrations 51 are formed between bar 42 and upper platen 40. Serrations 51 are also parallel to claw 49 and are tilted toward the leading edge. A portion 52 of the printing plate between printing surface 48 and serrations 51 angles upwardly. To remove the printing plate from the mold after material 47 has hardened into a solid, upper platen 40 is raised and the printing plate is peeled off by directing a stream of air between it and intermediate mold 44. Then, upper platen 40 is returned the angle the position shown in FIG. 2 to prepare a duplicate printing plate. To remove intermediate mold 44, bars 42 and 43 also are raised.

FIG. 3 is an enlargement of leading edge 24 of printing plate 23. Leading edge 27 of printing plate 26 is identical thereto. A transversely elongated front hook 60 made from a piece of spring steel extends across printing cylinder 10 adjacent to leading edge 24 and parallel to the axis of rotation of printing cylinder 10. One end of hook 60 is attached to the bottom of saddle 12 by fasteners such as those designated 61 and 62. The other end of hook 60 engages claw 49 to fix leading edge 24 relative to saddle 12 in the direction toward trailing edge 25. The end of saddle 12 is sloped to match the angle of portion 50.

FIG. 4 is an enlargement of trailing edge 28 of printing plate 26. Trailing edge 25 of printing plate 23 is identical thereto. A transversely elongated rear hook 63 made from a piece of spring steel extends across printing cylinder 10 adjacent to trailing edge 28 and parallel to the axis of rotation of printing cylinder 10. One end of hook 63 is attached to the bottom of saddle 13 by fasteners such as those designated 64 and 65. The other end of hook 63 engages one of serrations 51. Since serrations 51 are tilted toward the leading edge, the trailing edge of printing place 26 is fixed relative to saddle 13 in the direction toward the leading edge and is free to move relative to saddle 13 in the direction away from the leading edge, i.e. serrations 51 and the end of hook 63 form a ratchet arrangement. The end of saddle 13 is sloped to match the angle of portion 51.

As blanket cylinder 11 presses against the printing plates during operation of the rotary printing press, the slack in the printing plate is pushed toward its trailing edge. When the slack reaches the trailing edge, it is taken up by the ratchet arrangement, in that a different one of serrations 51 engages the end of hook 63. As a result, all the slack is taken out of the printing plates and the printing plates are held in tension on their respective saddles, which makes them in effect as rigid as a lead printing plate despite their flexibility. It is not necessary to fix claw 49 relative to the saddle in the direction away from the trailing edge because the only force exerted on the leading edge of the printing plate is applied in the direction of the trailing edge.

To install' a printing plate on its saddle, the leading edge is first inserted into the space that front hook 60 encloses by moving portion 50 down in the direction of an arrow 66 in FIG. 3 so claw 49 clears the gap between the end of front hook 60 and saddle 12. After claw 49 engages front hook 66, the printing plate is extended around the saddle and the trailing edge is inserted into the space that rear hook 63 encloses to establish the ratchet arrangement by engaging the end of hook 63 with one of serrations 51. As cylinders 10 and 11 rotate, the printing plate is placed in tension.

Circumferential registration of the printing plates is insured by the fact that claw 49 is parallel to serrations 51 and front hook 60 is parallel to rear hook 63. A key arrangement between the leading edge of the printing plate and forward hook 60, which is shown in FIG. 5, establishes transverse registration of the printing plate. A notch 70 is formed at the middle of claw 49; and a finger 71 is formed in the middle of front hook 60. Finger 71 fits into notch 70, but does not permit claw 49 to pass into the space enclosed by hook 60 behind finger 71.

The permanent deformation of portions 50 and 52 and the matching slopes at the ends of the saddle eliminate any internal stress or external force by the supporting surface of the saddle that might otherwise tend to make the printing plate buckle or bulge when it is bent at its edges to engage the hooks.

Since the front and rear hooks are the same, the press could be run in the opposite direction, i.e. the direction of rotation of cylinders 10 and 11 could be reversed. In such case, the printing plates would also be reversed so the claw forms the leading edge and the serrations form the trailing edge. Further, the notch would be formed at the center of the serrations instead of the claw.

The described embodiment of the invention is only considered to be preferred and illustrative of the inventive concept. The scope of the invention is not to be restricted to such embodiment. Various and numerous other arrangements for securing the flexible printing plate in the described manner may be devised by one skilled in the art without departing from the spirit and the scope of this invention as defined in the claims. Further, the saddles can be eliminated if the printing press is especially designed for thinner printing plates. In the claims, the term printing cylinder is taken to include a saddle if needed.

What is claimed is:

l. A printing system comprising:

a rotating printing cylinder;

a flexible printing plate disposed on the surface of the printing cylinder to form a leading edge that rotates in advance of a trailing edge;

means for securing the leading edge of the printing plate to the printing cylinder so the leading edge is fixed relative to the printing cylinder in the direction toward the trailing edge;

a plurality of transversely elongated parallel serrations extending along the trailing edge of the printing plate;

a rotating blanket cylinder disposed adjacent to the printing cylinder to press against the printing plate, the printing plate and the blanket cylinder rotating together in non-slipping relationship;

transversely elongated rear hook means fixed relative to the cylinder and extending across the cylinder adjacent to the trailing edge of the printing plate, the rear hook means being adapted to engage the serrations so the trailing edge of the printing plate can move across the rear hook means in the direction away from the leading edge without moving in the direction toward the leading edge, thereby securing the trailing edge of the printing plate and tensioning the printing plate as the cylinders rotate; and

a web of paper guided between the printing plate and the blanket cylinder where the blanket cylinder presses against the printing plate.

2. The system of claim 1, in which the means for securing the leading edge comprises a transversely elongated claw extending along the leading edge of the printing plate and a transversely elongated front hook extending across the printing cylinder adjacent to the leading edge of the printing plate, the claw and the front hook engaging each other to secure the leading edge of the printing plate.

3. The system of claim 2, in which the front and rear hooks are parallel to each other and the claw and the serrations are parallel to each other.

4. The system of claim 3, in which the printing plate has a printing surface disposed between the claw and the serrations and the front and rear hooks are set below the printing surface.

5. The system of claim 4, in which the portion of the printing plate extending between the printing surface and the claw and the portion of the printing plate extending between the printing surface and the serrations are permanently deformed to angle inwardly toward the hooks to prevent buckling of the printing plate when the claw and the serrations engage their respective hooks.

6. The system of claim 5, in which the surfaces of the printing cylinder under the permanently deformed portions of the printing plate are sloped to match the angle of the permanently deformed portions of the plate.

7. The system of claim 6, additionally comprising means for positioning one edge of the printing plate laterally with respect to the corresponding hook to effect transverse registration of the printing plate on the printing cylinder.

8. The system of claim 7, in which the means for positioning one edge of the printing plate laterally comprises a discontinuity in the center of the front hook preventing engagement of the claw and a corresponding notch at the center of the leading edge of the printing plate that engages the discontinuity.

9. The system of claim 8, in which the printing cylinder comprises a base cylinder and a matching saddle secured to the base cylinder, the printing plate is disposed on the saddle, and the hooks are disposed on the base cylinder.

l r j CERTIFICATE OF CORECTION "Patent 2,281 Dated January 1, 1974 Inventor-(s) JOhfi C. Darnell, Jr

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

- On the front page, correct the name of the assignee to "The Times l lirror Company. 1

Signed end sealed this 19th dey of November 1974.

. (SEAL) Attest:

-McCOYM; GIBSON JR,

Attesting Officerc. MARSHALL DANN Commissioner of Patents 

1. A printing system comprising: a rotating printing cylinder; a flexible printing plate disposed on the surface of the printing cylinder to form a leading edge that rotates in advance of a trailing edge; means for securing the leading edge of the printing plate to the printing cylinder so the leading edge is fixed relative to the printing cylinder in the direction toward the trailing edge; a plurality of transversely elongated parallel serrations extending along the trailing edge of the printing plate; a rotating blanket cylinder disposed adjacent to the printing cylinder to press against the printing plate, the printing plate and the blanket cylinder rotating together in nonslipping relationship; transversely elongated rear hook means fixed relative to the cylinder and extending across the cylinder adjacent to the trailing edge of the printing plate, the rear hook means being adapted to engage the serrations so the trailing edge of the printing plate can move across the rear hook means in the direction away from the leading edge without moving in the direction toward the leading edge, thereby securing the trailing edge of the printing plate and tensioning the printing plate as the cylinders rotate; and a web of paper guided between the printing plate and the blanket cylinder where the blanket cylinder presses against the printing plate.
 2. The system of claim 1, in which the means for securing the leading edge comprises a transversely elongated claw extending along the leading edge of the printing plate and a transversely elongated front hook extending across the printing cylinder adjacent to the leading edge of the printing plate, the claw and the front hook engaging each other to secure the leading edge of the printing plate.
 3. The system of claim 2, in which the front and rear hooks are parallel to each other and the claw and the serrations are parallel to each other.
 4. The system of claim 3, in which the printing plate has a printing surface disposed between the claw and the serrations and the front and rear hooks are set below the printing surface.
 5. The system of claim 4, in which the portion of the printing plate extending between the printing surface and the claw and the portion of the printing plate extending between the printing surface and the serrations are permanently deformed to angle inwardly toward the hooks to prevent buckling of the printing plate when the claw and the serrations engage their respective hooks.
 6. The system of claim 5, in which the surfaces of the printing cylinder under the permanently deformed portions of the printing plate are sloped to match the angle of the permanently deformed portions of the plate.
 7. The system of claim 6, additionally comprising means for positioning one edge of the printing plate laterally with respect to the corresponding hook to effect transverse registration of the printing plate on the printing cylinder.
 8. The system of claim 7, in which the means for positioning one edge of the printing plate laterally comprises a discontinuity in the center of the front hook preventing engagement of the claw and a corresponding notch at the center of the leading edge of the printing plate that engages the discontinuity.
 9. The system of claim 8, in which the printing cylinder comprises a base cylinder and a matching saddle secured to the base cylinder, the printing plate is disposed on the saddle, and the hooks are disposed on the base cYlinder. 